The invention relates to apparatus for cutting stiff sheet materials, such as hardboard and paperboard. It can be used to cut other material, including thin, light sheet metal, such as shim stock, if desired.
When sheets of hardboard or mounting board are to be cut, it is important that they be cut truly and straight, at 90.degree. to the surface, and that the cut not deviate from a straight line. It is also important for the cutting to be done without having to exert great physical force.
Cutting devices of the type known as paper cutters that have a hinged blade, tend to deviate from a straight line, especially with very large sheets. They are very expensive for large sheets and tend to be very difficult to operate. They are quite unsatisfactory for use with hardboard, because they require too much force to be supplied by the operator.
Cutters having a single disc blade are normally unable to cut thick or hard sheets of material satisfactorily and tend to produce a non-linear edge as well as not to provide a straight cut through. The blade is usually somewhat cocked to the angle of the cut and achieves a straight cut-through for only one or so thicknesses.
Shearing apparatus such as are shown by the Wheeler et al, U.S. Pat. No. 3,706,251, involves the use of motors to cut sheet metal. They would be difficult to operate manually. Even then, the results would not be satisfactory with materials such as cardboard, mounting board, and hardboard. That device relies on a series of rapid passes in which the assembly of cutting rollers is brought closer and closer to the opposite side of the material being cut. This action tends to crush and damage mounting board.
A device using a plurality of rollers which are successively closer is also shown in German Pat. No. 437,291 (1926). This rather inflexible device has a blunt anvil against which it moves, a piece of metal having an engaging angle at 90.degree., an angle which I have found to give generally unsatisfactorily results.
Neither of the devices just mentioned makes it easy to replace the rollers or to replace one series of rollers with another series for operation on thicker or thinner material.
Moreover, there has been no good cutter for material lying in between paper and metal. The small paper cutters cannot cut hardboard or even do well for large sheets of cardboard, while the heavy plant cutters for metal are both too expensive for and unsuited to cutting the cardboard and hardboard.
An important object of the present invention is to provide a cutting device for obtaining true linear cuts that cut straight through mounting board, cardboard, hardboard, and the like.
Another object of the invention is to provide a system that can easily be operated by hand, requiring comparatively little strength for cutting rather thick mounting board and hardboard.
Another object is to provide a small, wall-mounted progressive cutting device that can be hand operated, much less expensive than heavy-duty metal cutters, and comparable in expense with good paper cutters.
Another object is to provide a cutting device also suitable for leather, plastic, and other stiff materials having a rather soft or yielding surface. The device can also be used for cutting light sheet metal, if desired.
Another object of the invention is to provide a cutting device in which the blades and rollers are readily replaceable.